Method for Drying Spent Filter Media

ABSTRACT

Disclosed is a process of stabilizing spent filter material that comprises mixing the filter media with a dry media to produce a composition having a moisture content that is sufficiently low to retard microbial growth. The composition comprises spent filter media and a dry material, and preferably comprises diatomaceous earth. Soil is treated by adding the composition as a top dressing, soil amendment, or the like.

RELATED APPLICATION

This application claims priority to prior provisional application Ser.No. 60/681,173, filed May 16, 2005. The entire contents of thisapplication are hereby incorporated by reference in their entireties.

FIELD OF THE INVENTION

The invention relates to methods for treating spent filter media, inparticular filter media containing diatomaceous earth. In otherembodiments, the invention pertains to compositions that contain spentfilter media, and to associated methods. The compositions of theinvention are useful in various embodiments as top dressings, soilamendments, and fertilizers in lawn care applications.

BACKGROUND OF THE INVENTION

Vacuum filtration is a commonly used in the manufacture of a variety ofagricultural, food, beverage, and biotechnology industries. In additionto the fixed equipment, production scale vacuum filtration systems suchas rotary drum vacuum filters, leaf filters, and the like typicallyemploy process aids, which are also referred to as filtration aids.These consumable aids range from fibers, cloths, and the like toparticle materials such as clays, diatomaceous earth, carbon,cellulosics and associated materials and are used to coat the filters.These materials retain both insoluble and soluble impurities by variousphysicochemical means. Particulate materials are also sometimes added tothe prefiltration supernatants and subsequently recovered from thefilter as a high moisture filter cake as it accumulates on the filtersurface. A number of permutations of this approach are practiced in anarray of industries today. For example, diatomaceous earth (DE) is awidely used filter medium. Diatomaceous earth is frequently used, aloneor in conjunction with other process aids, to clarify water, beveragesincluding beers, wines, juices and the like, and also to clarify foodingredients such as maltodextrins, syrups and the like.

An undesirable and problematic aspect of filtration systems that employa filtration aid is the disposal of the used (spent) filtration aid.Because of the significant cost and time entailed in the recycling offiltration aids, generally the spent filter media is simply disposed ofin a landfill. However, disposing of this media in a landfill iswasteful and unproductive.

Materials that can be used in filtering aids often have otherfunctionalities and utilities. Diatomaceous earth also is widely used ingardening, landscaping, and potting soil mixes. Diatomaceous earth alsois used as a non-toxic, organic insecticide, where it is regarded as asafe alternative to chemical insecticides. For these applications, thediatomaceous earth is typically added as a dry mined powder. Thediatomaceous earth is typically added to the final gardening,landscaping, and potting soil mix and dry blended. In theseapplications, the diatomaceous earth typically is devoid of biomoleculessuch as carbohydrates and proteins or other extraneous matter.

Diatomaceous earth found in spent filter media is generally not suitablein such lawn and garden applications. The spent filter media contains asignificant amount of water, and generally also contains particulatesand other material such as carbon and nutrients retained from thefiltration stream. If the filter media is not dried or preservedimmediately, uncontrolled microbial growth can occur in the presence ofthe media. Such microbial growth generally will render the mediaunsuitable for lawn and garden applications. Diatomaceous earth may bedried, but known drying processes are deemed to be uneconomical in lawnand garden applications. Moreover, organic material entrapped in thediatomaceous earth often is undesirable. For example, organics aredeemed undesired in potting soil mixes and seed bedding soils.

Other approaches such as composting (as purportedly disclosed in U.S.Pat. No. 6,261,604) have been suggested, but these approaches have notbeen widely adapted. Composting is a slow, laborious process thatrequires substantial time and space. Moreover, although composting doesaddress some broad disposal issues, composting does not significantlyenhance the utility of the media.

Thus, the absence of a technology to efficiently recycle spent filtermedia reduces its value and causes users to incur disposal expense.

THE INVENTION

It has now been found that spent filter media, such as diatomaceousearth, may be stabilized by blending the filter media with a drymaterial to form a composition. A preferred source of dry material islime, but other ingredients, such as clays, binders, surfactants,minerals, fibrous plant materials, or fertilizer ingredients thatcontribute plant nutrients or micronutrients may be used in conjunctionwith the invention. The moisture content of the composition ispreferably sufficiently low to inhibit mold growth, and in preferredembodiments of the invention is below 18% by total weight. Thecomposition preferably is provided in the form of discrete pluralparticles, the particles taking the form of pellets or granulatedparticles.

The resulting composition, which preferably is biodegradable andnon-toxic is useful in many commercial applications. In particular, theinventive composition has utility in turf, landscape, gardening andagronomic and/or horticultural applications, such as top dressingtreatments, fertilizers, and soil amendments. The invention is deemed inpreferred embodiments to find utility in highly chemically treated soilwhere the microbial population/density is depleted. For many suchapplications, entrapped organic and biological materials are believed toenhance the functionality and value of the composition.

In many lawn and garden applications, materials such as peat moss,vermiculite, and perlite are used to provide soil aeration. Soilaeration compositions made with such materials are generally moreexpensive than those prepared in accordance with the preferredembodiments of the invention. The composition of the preferredembodiments of the invention may be used to provide soil aeration moreinexpensively than can be attained using the heretofore describedmaterials.

Methods of preparing a composition and methods of use of suchcomposition, such as those described in more detail hereinbelow, alsofall within the scope of some of the various embodiments of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It has been discovered that spent filter media, such as media containingdiatomaceous earth, can be processed directly as it is shed from thefiltration system. Although the present invention is contemplated to beapplicable to any suitable type of spent filter media, spent filtermedia that contains diatomaceous earth (such as that obtained from acommercial brewing process) is the preferred embodiment. In such cases,the filter media often will include other processing aids, such ascarbon, ion-exchange materials, surfactants and the like, in addition todiatomaceous earth. Preferably, 30 wt % or more of the composition,based on the dry weight of the ingredients in the spent filter media,comprises diatomaceous earth. Typically, the spent filter media willcontain about 30 to 95 wt % diatomaceous earth, about 10 to 50 wt %organic carbon, about 1 to 25 wt % activated carbon and about 20 to 50wt % water. Because the invention is deemed to be particularlyapplicable to such spent filter media, the invention is usuallydescribed herein with reference to same, although it is contemplatedthat a homogeneous spent filter medium (in particular exclusivelydiatomaceous earth) is useful in conjunction with the invention.

As supplied, spent filter media most typically contains 20 to 40 totalwt % water. In accordance with one embodiment, the present invention isdirected to a process of drying the spent filter material by forming acomposition that includes the spent filter media and a dry material, thecomposition having to a moisture content that is sufficiently low toprevent microbial growth during storage of the composition. In preferredembodiments, the composition includes at most 18% water by total weight;more preferably, the composition includes at most 15% water by totalweight; most preferably, the composition includes 10%-15% water by totalweight.

The filter media is blended with a dry material to form a composition.Any suitable dry material may be used in conjunction with the invention,and materials such as calcium carbonate, clays, lime, or the like may beemployed. When calcium carbonate is employed, the calcium carbonate maybe, and preferably is, applied in the form of lime, an ingredient thatis beneficial in that it is useful in adjusting the pH of certain soils.Agricultural lime generally comprises limestone crushed to a finepowder. Alternatively, calcium carbonate may be obtained from othersources, such as shells. Clays are particularly advantageous in thatmany clays serve to correct soil acidity. Mixtures of the foregoing orother suitable materials may also be used.

Prior to blending with the spent filter media, the dry material need notbe completely moisture-free, and in typical embodiments the dry materialincludes some moisture but is sufficiently low in moisture to dry thespent filtration medium to the requisite level of dryness. The drymaterial preferably includes less than 2 wt % moisture, and morepreferably less than 1 wt % moisture, based on the total weight of thedry material.

The dry material and spent filter media may be blended in any suitablefashion and in any ratio effective to dry the spent filter media to thedesired moisture content, which generally is an amount that will notsupport microbial growth. The dry material and spent filter media, alongwith other desired ingredients, are blended to produce a compositioncontaining 5% to 90 wt %, preferably 40% to 70%, more preferably 40 to60%, spent filter media based on dry solids weight. Typically, the drymaterial is present in amounts of about 15 and 60 wt % based on thetotal weight of the filter media and the dry material.

Other ingredients may be incorporated into the dried composition. Forinstance, the composition may include binders, such as ironlignosulfonate or another lignosulfonate. Iron lignosulfonate, used as abinder, also provides the soil with mineral iron. When used, the bindershould be added in amounts effective to attain a binding effect,typically about 2 to 30 wt % based on the total weight of the driedcomposition. Alternatively, or in addition thereto, the composition mayinclude a surfactant. Natural surfactants, such as yucca extract, arepreferred. When used, the surfactant should be added in any amounteffective as a surfactant. In the case of yucca extract, 0.05 to 1.5 wt% yucca extract is added, typically about 0.3 wt %, based on the totalweight of the dried composition.

One or more additional plant materials may be incorporated into thecomposition, such as corn fiber, alfalfa and the like. These materialspreferably are added after the dry material and diatomaceous earth areblended. Such materials are deemed suitable as pelletizing aids when thecomposition is supplied as a pelletized composition, and may be added inamounts suitable therefor. Some such materials, such as alfalfa, provideadditional nutritive benefit to the composition.

In some embodiments, the dry material comprises or incorporates anadditional plant nutrient. Useful plant nutrients include but are notlimited to urea, phosphate, and other macro- and micro-nutrients. Whenused to augment another dry material, the plant nutrient may be presentin any suitable amount effective to obtain the desired organic ornutritive value. One suitable nutrient is SOLULAC™, sold by GrainProcessing Corporation of Muscatine, Iowa. SOLULAC™ comprises corn fiberaugmented with distillers grain solubles. When used, typical amounts ofSOLULAC are about 2 to 30 wt %, based on the total weight of thecomposition.

When intended as a fertilizer, the composition may include any suitableingredients. Preferred ingredients include nitrogenous materials, suchas urea. Such materials may be present in any suitable amounts.

A composition prepared as discussed hereinabove may be provided to auser in any suitable form. For instance, the composition may be providedas a powder or “meal,” prepared simply by blending the above-describedingredients. Preferably, however, the composition is provided in theform of pellets, by which is contemplated the pellets made using aconventional pelleting mill or similar apparatus that adds heat and/ormechanical energy in an extrusion process. During the pelleting process,heat may be added as needed to facilitate pelleting. The pelletedmaterial is then cooled and, preferably, the particle size is reduced,such as by crumbling. Upon pelleting, the preferred particle size isabout 7-20 mesh and more preferably 9-12 mesh. The moisture content ofthe pellets so prepared is preferably 10% or lower. Alternatively, theproduct may be provided in the form of granulated particles preparedwith a suitable binder.

The invention is also directed to a method of treating soil. The methodcomprises adding to the soil a composition comprising spent filter mediaand a dry material as discussed hereinabove. The composition may beadded as a fertilizer, a top dressing, or a soil amendment. A pelletedproduct prepared in accordance with the foregoing teachings isparticularly suitable for use as a top dressing. The top dressing may beapplied by spreading the composition onto a surface using any suitableapparatus and in any amount desired, such as an amount effective toinhibit insecticidal growth on the soil, to aerate the soil, or to addnutritive value to the soil. The pelleted product may be spread inamounts ranging, for instance, from 0.5 lb/1000 sq. ft. to 60 lb/1000sq. ft. One suitable spreading apparatus is a rotary spreader.Alternatively, the composition may be applied after manually aerating asoil bed or turf area.

The following non-limiting examples are provided for illustration.

EXAMPLE 1

A spent filter material (filter cake) was recovered from a rotary vacuumfilter. The filter material contained about 35% DE, 22% organic carbon,12% activated carbon and 31% water. The filter material was added to alaboratory mixer and homogenized. About 20% calcium carbonate was thenadded, and the mixture thus formed was thoroughly blended.

After a few minutes of further mixing, a dry animal feed product,SOLULAC™ (Grain Processing Corp., Muscatine, Iowa) was added in anamount of about 20% by weight of the mixture. The final compositioncontained about 60% filter cake, 20% calcium carbonate and 20% SOLULAC Ameal was formed. The moisture content of the meal was about 15.5%.

The meal thus prepared was pelleted using a pilot scale pellet mill. Themoisture content of the pellets was about 14%. After cooling overnighton a flat surface, the moisture content of the pellets was about 4.7%.The pellets were packed in 5-gallon pails.

EXAMPLE 1A

Example 1 was repeated up to the point of formation of a meal, exceptthat corn bran was used instead of SOLULAC. The moisture content of themeal was 12.5%

EXAMPLE 2

A spent filter cake comparable to the material used in Example 1 (DE,carbon and entrapped organics) was incorporated in a composition asfollows:

Spent filter cake 50% SOLULAC 10% Fe Lignosulfonate 20% CalciumCarbonate 19.7%   Yucca Extract 0.3% 

As in Example 1, the composition, which had a moisture content of about12.7%, was thoroughly blended and pelleted using a pilot scale pelletmill. The pellets exhibited good integrity and hardness. The pelletswere cooled overnight and available for packaging the next day.

EXAMPLE 3

A composition was prepared as follows:

Spent filter cake* 40% SOLULAC 10% Powdered Lime 49.7%   Yucca Extract0.3%  *composed of DE carbon; and organics

The components were blended and pelleted as in Examples 1 anal 2.

EXAMPLE 4

The meals of Examples 1, 2 and 3 were pelleted using a pilot CaliforniaPellet Mill. The compositions, which typically ranged from 15% to 13%moisture, were blended and fed into the mill as is. A pellet die with0.156 times 1 inch openings was employed. The pelleting temperature was83-85° C. The temperature of the pellets immediately recovered from themill was about 118° C. The hot pellets were then collected and cooledovernight at room temperature. The final pellet moisture ranged from 5%to 9%.

EXAMPLE 5

Spent filtration material from Grain Processing Corporation (Muscatine,Iowa) was collected and delivered to a production scale, fullyintegrated mixing-pelleting and finishing line. The spent material wastransferred to a large mixing vessel, generally from 12-36 hours afterdelivery.

Dry calcitic limestone (1-2% moisture) was added to the vesselcontaining the spent filter cake. This mixture was mixed for at least 30minutes (longer blending times being preferred to provide greaterhomogeneity and to reduce the formation of aggregates). After achievinga relatively uniform mixture, and while still mixing, alfalfa meal wasadded to the mixer. The spent filter cake, limestone and alfalfa mealmixture was then blended for at least another 30 minutes. The blendedcomposition, which was composed of approximately 60% spent cake, 20%limestone/calcium carbonate and 20% alfalfa meal, was conveyed to acommercial feed pelleting line.

The mixture was pelleted using a 3/12″ pellet die. No steam orextraneous heat was added during the pelleting process. The formedpellets were cooled for about 20-25 minutes using an ambienttemperature, unconditioned air chamber (commonly referred to as a pellet“conditioner”). The pellets then were conveyed to crumbling machine,commonly referred to a “pellet crumbler,” which used rollers to reducethe pellets to a smaller particle size within the heretofore expressedpreferred range.

The finished product, which had a moisture content of about 10%, wastransferred to holding vessels to await packaging. This productcontained activated carbon by virtue of the carbon present in theoriginal spent filter media.

EXAMPLE 6

A fertilizer is prepared using dried spent filter media and urea.

It is thus seen that the present invention provides a method for dryingspent filter media and a dried composition prepared upon drying thespent filter media. The process of the instant invention providesrecycling and adds value to what otherwise would be a waste filterproduct. The composition has utility in a variety of agricultural andlandscaping applications, as well as soil and compost products. Thecomposition is stable and resistant to spoilage and odor formation, andallows nutrients entrapped in the filter media and other materialspresent in the composition to be delivered to soil in numerousapplications. In addition, the composition improves soil attributes suchas porosity, drainage, and the like. The invention thus provides acomposition that may substitute for more expensive materials, such aspeat moss.

All methods described herein can be performed in any suitable orderunless otherwise indicated herein or otherwise clearly contradicted bycontext. The use of any and all examples, or exemplary language (e.g.,“such as”) provided herein, is intended to illuminate the invention anddoes not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention. This invention includes all modifications and equivalentsof the subject matter recited in the claims appended hereto as permittedby applicable law. Moreover, any combination of the above-describedelements in all possible variations thereof is encompassed by theinvention unless otherwise indicated herein or otherwise clearlycontradicted by context.

1-20. (canceled)
 21. A composition comprising 5 to 90 wt % spent filtermedia based on dry solids weight, a second material selected from thegroup consisting of calcium carbonate, clay, lime, or a mixture thereof,and at least one additional material selected from the group consistingof a binder, a surfactant, a mineral, a nutrient, and a fibrous plantmaterial, wherein the spent filter media comprises spent diatomaceousearth containing nutrients retained from a filtration stream, and thecomposition comprises at most 18 wt % water.
 22. The composition ofclaim 21, comprising 10-15% water by total weight.
 23. The compositionof claim 21, comprising 40 to 70 wt % spent filter media based on drysolids weight.
 24. The composition of claim 23, comprising 40 to 60 wt %spent filter media based on dry solids weight.
 25. The composition ofclaim 21, wherein the second material is at least one of calciumcarbonate or clay.
 26. The composition of claim 21, wherein the secondmaterial is lime.
 27. The composition of claim 21, wherein the at leastone additional material is a fibrous plant material.
 28. The compositionof claim 21, wherein the spent filter media contains about 30 to 95 wt %diatomaceous earth, about 10 to 50 wt % organic carbon, and about 1 to25 wt % activated carbon based on the weight of the spent filter media.29. The composition of claim 21, wherein the nutrient is a plantnutrient, and wherein the plant nutrient is present in about 2 to 30 wt% based on the total weight of the composition.
 30. The composition ofclaim 21, wherein the diatomaceous earth comprises organic materialentrapped within the diatomaceous earth.
 31. The composition of claim21, wherein the composition is pelleted, the pelleted compositioncontaining at least about 4.7% moisture.
 32. The composition of claim31, wherein the pelleted composition contains up to about 15% moisture.33. The composition of claim 31, wherein the spent filter media containsabout 30 to 95 wt % spent diatomaceous earth, about 10 to 50 wt %organic carbon, and about 1 to 25 wt % activated carbon based on theweight of the spent filter media.
 34. A product prepared by a processcomprising mixing spent filter media with a dry material selected fromthe group consisting of calcium carbonate, clay, lime, or a mixturethereof, and blending in an amount suitable to effectuate drying viasaid blending to produce a composition having a moisture content of 10to 15% by total weight, the spent filter media comprising spentdiatomaceous earth containing nutrients retained from a filtrationstream.
 35. The product of claim 34, wherein the spent filter mediacontains 30 to 40 wt % water prior to drying.
 36. The product of claim34, wherein the composition comprises 5 to 90 wt % spent filter mediabased on dry solids weight.
 37. The product of claim 36, wherein thecomposition comprises 40 to 70 wt % spent filter media based on drysolids weight.
 38. The product of claim 34, wherein the dry material isat least one selected from the group consisting of calcium carbonate andclay.
 39. The product of claim 34, wherein the dry material is lime. 40.The product of claim 34, further comprising at least one of a binder, asurfactant, a mineral, a nutrient, or a fibrous plant material.
 41. Theproduct of claim 34, wherein the spent filter media contains about 30 to95 wt %, about 10 to 50 wt % organic carbon, about 1 to 25 wt %activated carbon, and about 20 to 50 wt % water based on the weight ofthe spent filter media.
 42. The product of claim 34, the compositioncomprising a pelletized composition that contains at least about 4.7%moisture.
 43. The product of claim 43, wherein the pelleted compositioncontains up to about 15% moisture.